Optimization Model on the Effect of Clove Oil, Formaldehyde, and Chitosan Added to Batik Fabric Colored with Gambier (Uncaria gambir Roxb): Antifungal Properties and Stability

Triggered by the concept of sustainability, the use of natural dyes in batik fabric processing has increased recently. To inhibit fungus growth on batik fabric colored with natural dyes, either clove oil or formaldehyde was added as an antifungal agent. To increase the stability of the interaction between the antifungal agent and the batik fabric, chitosan was used as a crosslinker. A modified version of the standard tests American Association of Textile Chemists and Colorists (AATCC) 30 and Response Surface Methodology (RSM) was applied as the characterization method. The results showed that the growth percentage of fungi in Batik treated with either clove oil or formaldehyde was much lower than that in the control sample. Growth of Aspergillus niger could be prevented by about 32% using clove oil and 94% using formaldehyde. The optimal condition was obtained with 1% chitosan as a crosslinking reagent, 15.91 ppm of formaldehyde, and 60-min immersion time, with absorbance intensity of formaldehyde crosslinking solution and fungus growth areas being 0.159 and 2.47%, respectively.

The Intrinsically Disordered Region of ExbD is Required for Signal Transduction

ABSTRACTThe TonB system actively transports vital nutrients across the unenergized outer membranes of the majority of Gram-negative bacteria. In this system, integral membrane proteins ExbB, ExbD, and TonB work together to transduce the protonmotive force (PMF) of the inner membrane to customized active transporters in the outer membrane by direct and cyclic binding of TonB to the transporters. A PMF-dependent TonB-ExbD interaction is prevented by 10-residue deletions within a periplasmic disordered domain of ExbD adjacent to the cytoplasmic membrane. Here we explored the function of the ExbD disordered domain in more detail. In vivo photo-cross-linking through sequential pBpa substitutions in the ExbD disordered domain captured five different ExbD complexes, some of which had been previously detected using in vivo formaldehyde crosslinking, a technique that lacks the residue-specific information that can be achieved through photo-cross-linking: 2 ExbB-ExbD heterodimers (one of which had not been detected previously), previously detected ExbD homodimers, previously detected PMF-dependent ExbD-TonB heterodimers, and for the first time, a predicted, ExbD-TonB PMF-independent interaction. The fact that multiple complexes were captured by the same pBpa substitution indicated the dynamic nature of ExbD interactions as the energy transduction cycle proceeded in vivo. In this study, we also discovered that a conserved motif, (V45, V47, L49, P50), within the disordered domain was required for signal transduction to TonB and to the C-terminal domain of ExbD and was the source of its essentiality.ImportanceThe TonB system is a virulence factor for many Gram-negative pathogens including E-S-K-A-P-E pathogenic species Klebsiella pneumoniae, Acinetobacter baumannii, and Pseudomonas aeruginosa. Because the majority of protein-protein interactions in the TonB system occur in the periplasm, it is an appealing target for novel antibiotics. Understanding the molecular mechanism of the TonB system will provide valuable information for design of potential inhibitors targeting the system.

More than a Toxin: Protein Inventory of Clostridium tetani Toxoid Vaccines

Clostridium tetani is the etiological agent of tetanus, a life-threatening bacterial infection. The most efficient protection strategy against tetanus is a vaccination with the C. tetani neurotoxin, which is inactivated by formaldehyde-crosslinking. Since we assumed that besides the tetanus toxin, other proteins of C. tetani may also be present in toxoid preparations, we analyzed commercially available vaccines from different countries in respect to their protein content using mass spectrometry. In total 991 proteins could be identified in all five analyzed vaccines, 206 proteins were common in all analyzed vaccines and 54 proteins from the 206 proteins were potential antigens. The additionally present proteins may contribute at least partially to protection against C. tetani infection by supporting the function of the vaccine against the devastating effects of the tetanus toxin indirectly. Two different label-free protein quantification methods were applied for an estimation of protein contents. Similar results were obtained with a Total Protein Approach (TPA)-based method and Protein Discoverer 2.2 software package based on the minora algorithm. Depending on the tetanus toxoid vaccine and the quantification method used, tetanus neurotoxin contributes between 14 and 76 % to the total C. tetani protein content and varying numbers of other C. tetani proteins were detected.

Second-generation method for analysis of chromatin binding using formaldehyde crosslinking kinetics

ABSTRACTFormaldehyde crosslinking underpins many of the most commonly used experimental approaches in the chromatin field, especially in capturing site-specific protein-DNA interactions. Extending such assays to assess the stability and binding kinetics of protein-DNA interactions is more challenging, requiring absolute measurements with a relatively high degree of physical precision. We previously described an experimental framework called CLK, which uses time-dependent formaldehyde crosslinking data to extract chromatin binding kinetic parameters. Many aspects of formaldehyde behavior in cells are unknown or undocumented, however, and could potentially impact analyses of CLK data. Here we report biochemical results that better define the properties of formaldehyde crosslinking in budding yeast cells. These results have the potential to inform interpretations of ‘standard’ chromatin assays including chromatin immunoprecipitation, and the chemical complexity we uncovered resulted in the development of an improved method for measuring binding kinetics using the CLK approach. Optimum conditions included an increased formaldehyde concentration and more robust glycine quench conditions. Notably, we find that formaldehyde crosslinking rates can vary dramatically for different protein-DNA interactions in vivo. Some interactions were crosslinked much faster than the time scale for macromolecular interaction, making them suitable for kinetic analysis. For other interactions, we find the crosslinking reaction occurred on the same time scale or slower than binding dynamics; for these it was in some cases possible to compute the in vivo equilibrium-binding constant but not on- and off-rates for binding. Selected TATA-binding protein-promoter interactions displayed dynamic behavior on the minute to several minutes time scale.

Study on the Preparation of Chitosan-Based Resin

With chitosan as the raw material, a new type of resin material is synthesized through formaldehyde crosslinking. The effects of the reactant ratio, the reaction temperature, the reaction time, the stirring rate and the system pH on the cross-linking rate are studied in detail. The resin material is then characterized by means of IR. The experimental results show that the reaction occurs mainly on the amino and the hydroxyl of chitosan. The chitosan-based resin material with good properties of sphericity and acidresistivity can be prepared under the optimal experimental conditions, which are found to be 1:5 for the ratio of chitosan and formaldehyde, 60°C for the temperature, 1 h for the reaction time, 440r/min for the stirring rate and 10 for the pH.